Abstract

In the cylindrical Pitot tube, an opening at the critical angle with the flow gives the static pressure. For small-diameter tubes this critical angle is 39¼ deg for incompressible fluids in a certain range of turbulent flow. Using a wind tunnel, the distribution of pressure was measured on the surface of ⅛-in. and 3/16-in-diam cylinders at Mach numbers ranging from 0.13 to 0.87. The change in the pressure distribution on the surface of the cylinders was small in the range of Mach numbers up to 0.25. In this range the critical angle was constant, and a simple cylindrical Pitot tube would be convenient for direct measurements of static pressure. At the higher Mach numbers, particularly above 0.4, the critical angle increases above that for incompressible flow. The directional accuracy of the cylindrical Pitot increases as the Mach number increases.

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